This invention relates to a procedure for making dry and dust free enzyme granules particularly useful for use with laundry detergents. The manufacture of enzymatic washing and cleaning agents by incorporating powdered, highly active enzyme concentrates by mixing them with common cleaning agents is well known. The washing agents manufactured in this manner tend to form enzyme dusts which can cause dermatologic damage both to the manufacturer and the consumer of the enzyme powder containing washing composition.
Various enzyme formulations and processes for these preparations have been developed in an effort to alleviate the dusting problem. For example, German AS No. 21 37 042 discloses a process in which an extrudable enzyme containing formulation is extruded through a die onto the revolving plate of a spheronizing device to form spherical particles of the enzyme containing formulations which are optionally coated with a material designed to prevent dusting.
In U.S. Pat. No. 4,087,368, there is disclosed an enzyme granule formulation in which rods or spheres of an enzyme in admixture with magnesium alkyl sulfate and ethylene oxide are provided.
U.S. Pat. No. 4,016,040 discloses a method for the preparation of free-flowing substantially dust free, spherical enzyme containing beads prepared by blending a powdered concentrate of the enzyme with a binder in molten form and spraying droplets of the blend through a spray nozzle into cool air to solidify the droplets and form the beads.
In U.S. Pat. No. 4,242,219, there is claimed a process for the preparation of enzyme containing particles prepared by mixing the dry enzyme with a hydrophilic organic cohesive material, a building agent and a moisture regulating agent and mechanically dividing it into particles of the desired size and shape which are then coated with a water repellent material.
Another type of granular enzyme formulation is described in U.S. Pat. No. 4,009,076. This formulation is prepared by mixing the dry enzyme with a solid non-viable substance and optionally a cohesive organic material as binder to form an enzymatically active core. An enzyme slurry containing the cohesive organic material can be sprayed onto, for example, sodium tripolyphosphate in a mixer or an enzyme powder can be mixed with the sodium tripolyphosphate and the cohesive organic material sprayed onto it with subsequent extrusion through a die. The enzyme containing granule is sprayed with an aqueous solution containing a plasticized organic resin and then dried.
A process is described in DDR Pat. No. 0 151 598 in which sodium tripolyphosphate is sprayed with an aqueous enzyme solution and agglomerated in a cyclone apparatus. The agglomerates are removed from the cyclone apparatus while still wet and placed in a mechanical blender with a drying detergent formulation and intensively mixed.
In British Pat. No. 1,483,591, there is described a process for coating water soluble or water dispersible particles, including enzyme particles, using a fluid bed reactor. This reference involves a dust free coating technique for enzyme particles which have been granulated by other processes such as prilling or spheronizing whereas the process of this disclosure applies an active layer of enzyme onto an inert core.